When Dover vanishes from Scotland Yard, along comes an ultimatum from a gang of kidnappers. Not only do they want a stout ransom for his return, but also the release of two prisoners. What will become of our doubtful detective?

When Dover vanishes from Scotland Yard, along comes an ultimatum from a gang of kidnappers. Not only do they want a stout ransom for his return, but also the release of two prisoners. What will become of our doubtful detective?